A. Field of the Invention
This invention relates to the field of data communication and more particularly to a method of connecting a wireless user generating digital data (for example, a computer having a cellular telephone modem) to a computer network, such as a corporate backbone LAN or the Internet.
B. Description of Related Art
Network access servers that provide local or wide area network access for remote users dialing in over the public switched telephone network are known in the art. These devices are available from 3COM Corporation (previously from U.S. Robotics Access Corp.), the assignee of the present invention. The Total Control Network Enterprise Hub from 3COM is a representative network access server. It is described in U.S. Pat. No. 5,577,105 of Baum et al., entitled "Telephone Call Switching and Routing Techniques for Data Communications," and U.S. Pat. No. 5,528,595 of Walsh et al., entitled "Modem Input/Output Signal Processing Techniques." The Walsh et al. and Baum et al. patents are both fully incorporated by reference herein.
The network access server described in the Walsh et al. and Baum et al. patents provides an interface to a multiplexed digital telephone line, a plurality of modems for performing signal conversions for the data from the remote users, and a network interface for transmitting demodulated data from the modems onto a local or wide area network. A high speed midplane bus structure comprising a time division multiplexed bus provides a signal path between the channels of the telephone line and the modems. The high speed midplane also includes a parallel bus that couples the modems to the network interface.
This network access server architecture in a single chassis has proven to be very popular in a variety of applications, particularly corporate network access. The network access server is also particularly popular with Internet service providers for land-based Internet users. With a single network access server, the Internet service provider can handle a large number of simultaneous Internet access calls and provide full duplex communication between the multiple remote users and host computers on the Internet.
The technology for Internet access for wireless users is now emerging. There are two competing standards for wireless service, CDMA (Code Division Multiple Access, described in the standards documents IS-130 and IS-135, incorporated by reference herein) and TDMA (Time Division Multiple Access, described in standards document IS-99, also incorporated by reference herein). These standards specify a feature rich sets of digital wireless communications, for both voice and data. The two standards differ in how digital data from multiple users are multiplexed on the radio interface.
In accordance with both wireless technologies, a wireless user transmits data to a mobile switching center. The mobile switching center provides connectivity to the public switched telephone network, certain multiplexing and control functions, and switching functions for the mobile users. Multiplexed digital data from a plurality of remote wireless users is then capable of being transmitted via high speed communication formats (such as Frame Relay) to communication elements in the public switched telephone network.
The present invention provides for network access methods and apparatus that are particularly suitable for wireless users. The present invention also provides for network access methods by which a network access server, in combination with one or more authentication servers, can provide for Internet and corporate network authentication and access. The network access server provides for the functions needed for terminal equipment connected to a TDMA or CDMA mobile telephone to inter-work with terminal equipment connected to the public switched telephone network (PSTN) and the Internet. Further, the invention provides for Internet access methods for a plurality of remote users that are subscribers of more than one Internet service provider, thereby giving more flexibility in the ability of a particular Internet service provider to serve diverse Internet users.